As disclosed in, for example, Patent Document 1 below, a child lock mechanism of a vehicle door lock device includes: a base member adapted to be assembled to a door of a vehicle; a first lever rotatably assembled to the base member and adapted to be linked with a latch mechanism; a second lever rotatably assembled to the base member and adapted to interlock with an inside door handle; and an intermediate member arranged between the first lever and the second lever in a state in which the intermediate member is assembled to the first lever and is not assembled to the second lever, the intermediate member being allowed to be retained at an unset position or a set position. The child lock mechanism is structured in such a manner that, in a state in which the intermediate member is retained at the unset position, a movement of the second lever is transmittable to the first lever through the intermediation of the intermediate member, and in a state in which the intermediate member is retained at the set position, the movement of the second lever fails to strike the intermediate member and thus is untransmittable to the first lever.